TfNH
T O A N C H U Y D NVj NGANG
C U A GIANKHOAN TLT
N A N G(JACKUP)
PGS.TS Dinh Quang Cudng Vidn XSy dung Cdng trinh biin SV. Nguyen Nggc Vinh Hien (48 CLC) Trudng Dai hgc XSy dung
Tdm tat: BSi bSo dua ra cdng thUe xSe djnh ehuyin vi ngang eiia kit eiu mdng dd ehSn di cSc giSn jackup (Spudean) khi tinh toan Jackup, tU dd tinh duge he sd nin va giai bSi toan lam vide ddng thdi eua Spudean vdi dit nin. Phuang phap nSy sU dung cae phuang trinh eSn bing lue vS eSc kit qua nghidn eUu gin day vi quan he tai trgng vS biin dang eiia nin ed ki din kieh thudc ciia Spudean.
Summary: The purpose of this paper Is to give the recommended function to calculate the displacement of Spudean of Jack up and suggest the practice method to design Jackup structure based on interaction between soil and Spudean during the operation of Jackup. The recommended function would be based on equation of force equilibrium and the recent science result of seabed properties.
I . O A T V A N D E
Khi md hinh hda k i t eiu de tinh toan kit eiu gian ty nang (jackup), lien kit ndi da't eda he kit ed'u thudng dupe md ta Id ngam cdng hoac ngam dan hdi. Op edng eda eae Id xo dan hdi thudng dupe xae djnh bang cae edng thdc trong quy pham Na Uy [5] hoac quy pham cda My [6], khdng dae trung cho bat ky hinh dang nao eua Spudean.
Bdi bao ndy gidi thidu mpt phuong phap xae djnh chuyen vj ngang cua Spudean. Cae cdng thdc v i dja ky thudt cdng trinh bien dupe kham khao va trich d i n td kit qua nghien edu eua Butterfield va R.HousIsby [1].
2. TiNH T O A N C H U Y E N Vj NGANG Cac gia thiet:
- Kit eiu khdi thupng tang cua jackup (Hull) tuydt dd'i cdng, vat lieu dan hdi tuyin tinh.
- Khi khdng k i de'n anh hudng cda tai trpng sdng vd gid tae ddng ldn k i t ed'u thi tai trpng thupng ting (W) dupe chia deu eho ba Spudean (hinh 2).
lai trpng ngang dupc ky hieu la Hj dupe dat tai tog dp L' = L + S + Y, ede khoang cdch L,S,Y dupe danh d i u vd ky hidu nhutren hinh 2.
Trong mat bing ba chdn dupc sap xd'p theo hinh tam gide d i u . Chan 2 vd 3 d vj tri dd'i xdng qua dudng tmng tuyen td dinh Id chan 1 va dupc gia thiit Id ed chuyin vj vd chiu tai trpng nhu nhau.
- Bd qua chuyin vj xoay eua spudean so vdi day biin khi chju tai trpng ngang.
Hinh 1. Jackup vS cac ngoai luc tae dung Idn jackup
INP CHf KHOA HOC C O N G NGHt XAY DUNG SO 3/2008 83
Xet he kit cau eho tren hinh 1, vdi cdc gia thiit ndu trdn ddy thi Hull chi djch chuyin ngang song song vdi day biin dudi tac dyng cda tai trpng ngang Hj, chuyen vj ndy dupe ky hidu Id h^.
Cac gid trj ehuyen vi ngang tuong dd'i khde dupe ky hidu nhu hinh 3.
^Huii =^^^+^^= b,, + ^23
Trong do: h23 = hj = h^ va 823 = 62 = 83
2.1 Tinh toan chuyen vj ngang tuong do'i cua Hull va Spudean
(1)
vf^"! "1 ' v L / "
Hinh 2. Sa dd ting thi tinh toSn Jackup Hinh 3. Sa dd tinh chuyin vi thing vS vj xoay cUa Jackup Xet cdn bing lye ddng vd lyc ngang (hinh 2) ta dupc:
H,=H,+2H23
Trong dd: H23 = H2= H3 va V23= Vj = V3
Xet can bing mdmen tai diem thieh hpp trdn Spudean, ta suy ra dupc phuong trinh cdc phan lyc tai Spudean, cac ehd giai vd diu qui Udc dupc ghi tren hinh 2, chd y ring 5^
t h i khdc nhau. Phuong trinh xdc djnh cdc phan lyc diJng V,, V23=V2=V3 dupe viit nhu sau:
V,
W,(DI3 + S2,-e2,) + Hr.L D + (e,-e23)-(<J,-<523) _ W.{DI3-SJ2 + e,l2)-Hj.L
^23= D + (e,-e2,)-(S,~S„)
Vdi D Id khoang each tren hinh chiiu bang gida ehan 1 vd chdn 2, 3 va L'=L+S+Y Ky hidu e1=M,/V, Id dp lech tam cda phan lye tai ehan 1, tuong ty eho 82 vd 63
Gde xoay 9, eda Spudean ed quan he vdi momen M, vd dp citng chdng xoin tuyin sau (hinh 4).
chuyin
(2) (3)
xac djnh vd 82 cd
(4)
(5) (hinh 2).
KRS.I nhu
84 TAP CHf KHOA HOC C O N G N G H $ XAY DUNG Sd3/2008
M,=Kt>s,0, (6) Chuyin vj tuong dd'i eda ehan theo phuong y so vdi diim ndi gida chdn vd Spudean phai thda mdn phuong trinh ddn hdi sau (hinh 4):
El. d'y
dx' ••H,,(L + S-x)-M, (7) Trong dd: El - dp edng chdng udn.
Tieh phan phuong trinh (7) mdt l i n theo X, xdc djnh gde xoay dy/dx tai x = L, thay gia tri dy/dx tai X = L cho mdmen trong phuong trinh (6) va thu gpn k i t qua ta dupe:
0, = H..I}
2EI
El 1 + 2 ^ 1 ( 8 )
Hinh 4. So dd tinh chSnJackup chju udn
Tieh phdn phuong trinh (7) hai lan, xdc djnh chuyen vj tuong dd'i tai x = L, quan tdm d i n chuyen vj xoay tUdng ddi 9,.S (hinh 4), thay ehuyin vi xoay tuong dd'i tai x = L cho chuyen vj xoay trong phuong trinh (8), ta dugc:
S.= H..L'
^2EI 1 + 3 El
(1 + 2.S/L)' (9)
2.2 Tinh todn chuyen vj ngang cua Spudean - bai toan trupt ngang
Ung dyng cac k i t qua nghien edu eda Dean E.T.R, James, Tsukamoto [2], hinh 5 md ta quan hd tai trpng vd biin dang eda n i n ed k i d i n kieh thude cda Spudean.
Md'i quan hd giiJta md men vd phan lye ddng tai Spudean vdi dudng kinh Spudean nhu sau:
M,
+ ^ ' V^
(10)
Trong dd: B - Oudng kinh eda Spudean hinh trdn;
VM, - Kha ndng chju lUe theo phuong ddng hidn tai eda Spudean;
a, p - Cdc dai IUpng hing sd khdng thd nguydn phy thude vao hinh dang Spudean vd hd sd ma sdt giiia Spudean vdi nin. Cae dai lupng khdng thd nguyen a vd p edn phy thudc vdo dp sdu c i m sdu vdo da't theo phuong thing ddng cda Spudean vd kha ndng chju c i t cda dd't nin.
Dean [2] da dua ra cdc gia trj a vd p nhu sau: a=0.35 vd p=0.625. SNAME [3] da sd dyng cdng thdc tuong ty vd dua ra a=0.3 vd p=0.625. Cac tinh toan dudi ddy lay cae gia tri a=0.35 vd P=0.625 theo Dean [2].
TAP CHf KHOA HOC C O N G N G H E XAY DUNG Sd3/2008 85
Tsukamoto [2] da phdt trien biiu thdc cua Dean de xdc djnh M, vdi gia thiit quan hd gida md men tai Spudean M, vd gde xoay cda Spudean 9, vdi tai trpng theo phuong ddng tac dyng Idn Spudean la hang sd V, (hinh 5):
M. = M,„ 1-exp
[M,,rilB (11)
MylB i.
MmryB
m"' v,.v.
- ^
3. MOT SO KET QUA BAN DAU
Theo dd thi d hinh 5 vd bieu thdc (10) tinh dupc MULT cd gia tri nhusau
V,
0
D j d o g g i d i ban d a a h6i
. X y = V,
'i \ '""
Ma.r,, _^^y. V,.,
B V„. (12)
1 +
^ 1 JL
S )H.Rdt gpn cdng thdc (12) ta dupe:
V, Hinh 5. Quan he tii trgng vS biin dang
ciia nin ed kiden kich thudc eda Spudean
MULT,. ^ V.
B V^.
1 -
\ / , 4 ,
(13) 1 +
Vdi Q=(M/B)IH, va vdi gia trj KRE, dupe gia thiet Id phy thude tai trpng theo phuong ddng Idn Spudean thdng qua he sd RR^:
'^RE.i = ' ^ R E , l \ / ^
Quan he gida tai trpng vd bie'n dang tren hinh 5 dupc bieu didn nhu sau [2]:
A{B,0,) _M,IB A ( / 7 / / ? ) " 7 H 7
Vdi gia trj B vd p Id hang sd, thyc hien khai trien phdp tinh sd gia, h, dupe tinh nhu sau:
B',9,.J3'.H,
b. = •
M, Nhu vdy ta cd:
' ' t o l l = ' ' l + ^ 1 = /I23 't' '^23
B\0,,p^.H, H,,L '
M. 12£/ 1 + 3 El
EI + K„„.L {^ + 2.slLf
(14)
(15)
(16)
(17) (18) Trong dd:
B (m) - Oudng kinh Spudean (m);
B - He sd phy thude dp nham gida Spudean vd n i n (theo Dean p=0.625);
H, (T) - Lye ngang tac dyng vdo chdn thd i;
86 TAP CHf KHOA HOC CONG NGHE XAY DUNG
Sd3/2008
M, (Tm) - Md men do tai trpng ngang gdy ra tai diem tiip xdc chdn thd i vd nin;
l-(m) - Khoang each gida thupng ting (Hull) vd diim dau eda Spudean;
El (Tm^)- Op ciJng chdng ud'n cda chdn;
KRS , (Tm) - Od edng ehdng xoin cda chdn thd i;
S - Chiiu eao Spudean.
4. CAC BUdc TI'NH T O A N XAC DjNH CHUYEN Vj NGANG CUA SPUDCAN
Qua kit qua phan tieh trdn, cdng thdc (18) cd t h i tinh dupc chuyen vj ngang cda Spudean.
Tuy nhidn can phai cd npi lye ldn Spudean. Do vay phuong phap thyc hdnh d i tinh chuyin vj ngang dupc de nghj Id thuc hidn vide giai ldp kit cau va thue hidn theo cdc budc dudi day:
Budc 1: Tinh so bd dp cdng Id xo theo phuong ngang:
„ 8.G.R 2~v (theo DnV) k « ,x 32,h-v),G.R hode K, = — y — i (theo API)
Budc 2: Thyc hidn vide phan tich ddng k i t ca'u (ndn dung phin mim SACS V5.2).
Budc 3: Td k i t qua ndi lye, tinh todn Igi ehuyen vj ngang hHun theo edng thdc:
B'.0,,/3\H, H,,l}
1 + 3 El EI + K,,,L M, ^2EI
Budc 4: Tinh dp cdtig Id xo theo phuong ngang theo edng thdc:
' H \ ^
(l + 2.s/Lf
K.
\f^HULL.i "
vdi n IS si ChSn.
Budc 5: Tinh lap
Sau dd t h i K, vdo vd phan tieh ddng lan 2.
Budc 6: Kiem tra ket qua Ddng tinh toan khi K ; = K , " * ' 5. KET LUAN
- Cdc md hinh ddn gian thudng dugc sd dyng trudc day di tinh chuyin vj ngang cda cae gidn khoan tu ndng Id ngdm edng da td ra khdng chinh xae khi bd qua anh hudng eda dit nin.
- Cdc cdng thdc trong eae quy pham [5] vd [6] dang sd dung de tinh toan ehuyin vj ngang cua cdc gidn khoan ty ndng (jackup) da k i d i n anh hudng cda dd't nin tuy nhidn ehua xet den hinh ddng eua Spudean vd ehua ke d i n dp xuydn sdu cua Spudean vdo dd't nin.
- Bing vide dung cdc cdng thdc gidi thieu trong bdi bao ndy cd t h i xdc dmh dugc chuyin vi ngang cda Spudean vd tinh dupe sy Idm vide ddng thdi gida Spudean va dit nin, cd xet d i n hinh ddng eda Spudean vd dd xuydn sdu cda Spudean vdo dit nin.
TAP CHf KHOA HOC C O N G N G H $ XAY DUNG Sd3/2008 87
Tai lieu tham khao
1. Buttertield, R.HousIsby (1997) Standardized sign conventions and notation for generallly loaded foundations..Geotechnique Vol.47 No 5, trang: 1051-1054.
2. Dean,E.T.R, James, Tsukamoto (1993) - The bearing capacity of conical footings on sand in relation to the behavior of Spudean footings of Jackup. Nxb Oxford, Trang: 203-253.
3. Sname (1994) - Guidelines for site specific assessment of mobile jack-up units. Society of Naval Architects and Marine Engineers, Myc 5-5A, Nxb New Jersey.
4. Pierson, W.J and Moskowitz, L (1964) - A proposed form for fully developed wind seas based on the similarity theory of S.A Vol 69, No 24, Trang 518-902.
5. DnV, 1981, Rules for Design, Construction and Inspection of Offshore Structures, Hovik, Nonvay 6. API,1993, Recommended Practice for Planning, Designing and Constmcting Fixed Offshore Platfonns, American Petroleum Institute Publication RP-2A, Dallas, Texas
88 TAP CHI KHOA HOC C O N G N G H ^ X A Y DUNG Sd3/2008
